Given : (−4,5) is the coordinate of one vertex and 7x−y+8=0 is the equation of one of the diagonals of the square.We know that the diagonals of a square bisect at right angle.
∴ Equation of the other diagonal can be written as,x+7y+k=0We can check that (−4,5) does not lie on7x−y+8=0 as 7×(−4)−(5)+8î€ =0It means (−4,5) must lie on the other diagonal.∴−4+7×5+k=0⇒k=−31∴ Equation of the other diagonal is x+7y−31=0
